In the carton filling and sealing industry, particularly paperboard cartons used to package food, soap, etc., each carton travels along a conveyer path that is typically laid out in an elongated oval-shape with two parallel sides. At a carton feed station, located at one end of the oval, a carton feeding device connects each carton to a carrier unit secured to the conveyer line, with the elongated dimension of the carton oriented parallel with the travel path of the conveyer. As the conveyer advances the carton along one of the sides, flap guides hold open the major flaps at the bottom end of the carton, and an adhesive gun dispenses two patterns of adhesive on the spaced edges of the major flaps. These patterns are oriented perpendicular to the travel path of the conveyer. A caulk gun then dispenses a pattern of caulk on one of the major flaps, the caulk pattern being parallel to the travel path of the conveyer. Folding rails then fold the major flaps to seal the bottom of the carton. At the end of the first side, a filler fills the carton via the open upper end. Thereafter, the conveyer conveys the carton along the other side of the oval-shaped layout, and similar mechanisms operate to dispense adhesive and seal the upper end of the carton. A conveyer line of this type occupies about forty feet by twenty feet of floor space.
Generally, two types of adhesive dispensing systems have been used in carton filling and sealing operations of this type. These two types of systems are referred to as "contact" and "non-contact", depending upon whether or not a nozzle orifice of the system actually contacts the flaps of a carton when the adhesive is applied thereto.
For many years, contact adhesive dispensing systems have been the most popular in the carton filling and sealing industry. In contact adhesive dispensing, the system includes a doctor blade assembly which remains in contact with the carton flap, and therefore it is easy to coat a relatively large area with a large continuous bead of adhesive. Typically, the doctor blade assembly includes a backplate, a shim and a front plate which bolt directly to a gun body and adapter assembly. The gun body includes at least one internal conduit and a control mechanism for supplying pressure for controlling the flow of adhesive through the conduits, through aligned passages and an outlet channel in the adapter and finally, into and through passagways in the doctor blade assembly. The passageways open to a spacing between the front and the back plates where the shim has at least one cut-out region. The width of this spacing is determined by the thickness of the shim.
Particularly for cartons which, because of their contents, must have an infestation-proof seal, i.e., a continuous, relatively thick stripe of adhesive sufficient to prevent ingress of insects, contact dispensing guns remain popular because they provide the greatest certainty in achieving a consistent and reliable infestation-proof seal. Moreover, because of the structural components used to apply the adhesive, i.e., the doctor blade assembly, contact adhesive dispensing systems are not susceptible to clogs and therefore may be used with adhesives having a wide range in viscosity.
One primary disadvantage of contact adhesive dispensing systems relates to carton jams along the conveyor line. Because contact dispensing inherently requires direct contact between the doctor blade assembly and the flaps of the box, the relative positions of the entry and exit flap guides and the doctor blade assembly must be maintained securely in proper position throughout the operation. If one carton flap jams against the doctor blade assembly, the entire conveyor line must be shut down, the partially sealed cartons must be removed from the line and discarded, and the entire conveyor line must be restarted. In short, due to its inherent susceptibility to jamming, contact adhesive dispensing systems result in excessive conveyor downtime and a large number scrap cartons which cannot be reused.
In non-contact adhesive dispensing, a plurality of small nozzle tips spray the adhesive in a plurality of parallel streams onto the flaps of the carton from a distance of about a quarter inch to an inch. Usually, the nozzle tips are arranged in a row, and the rows are oriented perpendicular to the travel path of the conveyor. This produces an elongated stripe pattern comprising a plurality of parallel adhesive lines oriented perpendicular to the elongated dimension of the pattern. The nozzle tips are housed within the outlets of passageways in a nozzle plate. The nozzle plates secures to the adapter with inlet ends of the passageways in alignment with the outlet channel of the adapter.
Because of the spacing between the nozzles and the flaps, carton jams seldom occur. For these and other reasons, the carton filling and sealing industry has gradually moved toward more use of non-contact dispensing for forming siftproof seals, i.e., seals which must prevent egress of contents, such as macaroni, etc. Nevertheless, there remains a need for contact-type dispensing guns, particularly when an infestation-proof seal is required or for use with adhesives of relatively high viscosity.
Additionally, for various economic reasons, including changing marketing concepts and present tax treatment of stock, or inventory, it is no longer advantageous for carton filling and sealing companies to maintain multiple dedicated conveyor lines, with each line dedicated to one particular product and/or carton size and shape. As a result, conveyor lines must be adapted to accommodate different sizes and shapes of cartons and different types of adhesive dispensing and sealing operations.
It is an objective of this invention to reduce the downtime associated with changing a carton filling and sealing conveyor line from one type of adhesive dispensing to another type of adhesive dispensing.
It is another objective of this invention to expand the capability of a dispensing system used in a carton filling and sealing operations to a wider variety of carton sizes and shapes and/or a wider variety of dispensing operations.
The above-stated objectives are achieved by an adhesive dispensing system adapted to be easily converted between contact adhesive dispensing and non-contact adhesive dispensing, and vise versa, via a clamp which releasably secures to a gun body to compressively hold either a doctor blade assembly or a nozzle plate in contact with an adapter mounted to the bottom of the gun body. The profile of the doctor blade assembly and the nozzle plate are identical in size and shape to fit securely between the adapter and the clamp when the clamp is bolted to the gun body.
By loosening the clamping plate from the gun body, the doctor blade assembly or the nozzle plate may be removed from between the clamp and the adapter, and another doctor blade assembly or nozzle plate may be located therebetween and secured therein by again tightening the clamp against the gun body.
By providing identical profiles for a nozzle plate and a spreader blade assembly, and a clamp for securing either one of these identically shaped profiles to the gun adapter, the dispensing gun may be quickly and easily converted between contact-type adhesive dispensing and non-contact type dispensing, and vise versa.
Because of the structural arrangement of the clamp with respect to the gun body, the gun adapter and the nozzle plate or the doctor blade assembly, this invention reduces the downtime associated with converting a conveyor line from one type of dispensing operation to another. Thus, in addition to enabling relatively easy conversion between contact and non-contact dispensing, this invention also facilitates changeover from one type of non-contact dispensing to another type of non-contact dispensing, or from one type of contact dispensing to another type of contact dispensing, as required when a different size or shape carton must be filled and sealed.
According to a preferred embodiment of the invention, this interchangeable contact/non-contact dispensing system includes a modular body, an adapter, two or more plug-in dispensing modules, a clamp and at least one interchangeable nozzle plate or doctor blade assembly. The modular body includes at least one internal conduit fed by an inlet connected to an adhesive supply line. These conduits communicate with inlets in the plug-in modules, and outlets of the plug-in modules communicate with passages in the adapter. The adapter passages communicate with an exit channel oriented transverse to the ends of the passages. The clamp clamps to a front face of the modular body, as by bolts, to compressively hold either the nozzle plate or the doctor blade assembly between the adapter and a bottom portion of the clamp. This securement arrangement locates inlet ends of passageways formed in the doctor blade assembly or the nozzle plate in alignment with the channel, thereby to allow adhesive flow therebetween. Pressurized adhesive conveyed through the modular body, the plug-in modules, the adapter and eventually into the channel is subsequently dispensed outwardly from these passageways formed in the nozzle plate or the doctor blade assembly.
For contact dispensing, the doctor blade assembly is used. The doctor blade assembly includes a backplate with passageways aligned in fluid communication with the channel, a shim and a front plate. The front and back plate sandwich the shim, and dispensing adhesive exits from between the front and back plates via one or more vertical slots or cut-outs formed in the shim.
For non-contact dispensing, a nozzle plate is used. The nozzle plate includes a plurality of parallel passages, each of which terminates at a nozzle tip which is spaced about one inch or less from the substrate.
For non-contact or contact dispensing, the clamp securely holds the nozzle plate or the doctor blade assembly, respectively, against the adapter, with the passageways in alignment with the channel so that dispensing may take place. The cross sectional profiles of the nozzle plate and the doctor blade assembly are identical so that the clamp provides sufficient compressive holding force during either non-contact or contact dispensing. Preferably, the clamp includes a rounded bottom. When the clamp is tightened to the gun body, this rounded bottom urges the nozzle plate or the doctor blade assembly in an upward direction rather and into alignment with the channel, rather than in a downward direction and out of alignment with the channel.
In operation, the clamp is loosened to allow the nozzle plate or doctor blade assembly to be removed from between the adapter and the clamp. A different nozzle plate or doctor blade assembly is then placed against the adapter, with the passageways of the new nozzle plate or doctor blade assembly located in alignment with the channel. The clamp is then tightened to secure the new nozzle plate or doctor blade assembly in place. Preferably, loosening and tightening of the clamp occurs via loosening and tightening of threaded bolts which are threadably received in the gun body.
Because of the relative ease in loosening the clamp, removing the nozzle plate or doctor blade assembly, substituting a new nozzle plate or doctor blade assembly and then retightening the clamp, this dispensing system simplifies the changeover process required to convert a carton filling and sealing line from one type of dispensing operation to another type of dispensing operation. This dispensing system also reduces the time required for this changeover process. Because of the simplification and the reduced time required for changeover, this dispensing system also reduces the costs associated with filling and sealing cartons.
According to another aspect of the invention, a non-contact dispenser may be operated at a higher pressure to produce a continuous stripe pattern of adhesive on a carton flap, rather than a plurality of thin parallel lines arranged in perpendicular to an elongated stipe pattern. This resulting continuous adhesive pattern resembles the pattern which could only previously be produced by using a contact dispensing system.
These and other features of the invention will be more readily understood in view of the drawings and the following detailed description.